How is it possible that, start up's run by college kids with funding around quarter of $200,000 build stuff and a business around them. So that not only do they build the product completely but also get money for further work.

Business is a business, business is hard, luck , timing and connections play a huge part

Start-up means peanuts for promise of future pay -- success not guaranteed

Also, building an app/website is a million times simpler than building a programming language, or a virtual machine for said language to run-on, or maintaining 20 years of backwards compatibility across many OS ....

Try running gitstats on perl.git